Disinfection byproducts are formed in drinking water supplies where chlorine reacts with organic molecules in the source water. A range of disinfection byproducts can be formed.

The Friends of the Earth report focused on the disinfection byproduct, Bromodichloromethane (BDCM).

“BDCM is a Trihalomethane”, said Friends of the Earth Land Use Researcher Anthony Amis. Water authorities in Victoria test for four Trihalomethanes, including BDCM, Chloroform, Bromoform and Dibromochloromethane.

BDCM is classfied by the International Agency for Research on Cancer as being a 2B (possibly carcinogenic to humans).

The information, sourced from Westernport Water via a Freedom of Information request revealed that BDCM, was detected at levels higher than World Health Organisation (WHO) guidelines more than 250 times across the Westernport Water network between the years 2005-12.

Several areas of Phillip Island recorded levels of BDCM above WHO guidelines for several years. The eight year averages for the following communities were of most concern: Cowes, Ventnor, Sunset Strip and Rhyll.

The BDCM issue appears to have been recently lessened by the use of the chloramination process throughout 99% of the Westernport Water distribution system.

The National Health and Medical Research Council has not reviewed the trihalomethane guideline since 1996 and does not look at individual trihalomethanes, but rather the sum of four trihalomethanes. As such individual trihalomethane levels, such as BDCM, are not covered under the Australian Drinking Water Guidelines. Westernport Water were therefore not under any obligation to report the breaches of BDCM to Victorian Health authorities.

The Australian Drinking Water Guidelines do not take into account exposure to disinfection byproducts through the skin or by inhalation. Showering or bathing in water with high levels of disinfection byproducts can be a major source of exposure.

“Australian guidelines for trihalomethanes are set at levels over 3 times higher than equivalent United States guidelines. All areas in the Westernport Water network averaged 8 year THM levels, exceeding similar US guidelines, some by over 2.5 times. It is also apparent that many other communities across Australia would be consuming potentially dangerous amounts of disinfection bypoducts, particularly in times of low rainfall. Why are water consumers not being told about these byproducts. People at higher risk may be pregnant women, young children and people with chemical sensitivities and compromised immune systems” concluded Mr Amis.